In general, polyolefin resins have excellent physical and chemical properties and have widely been used as materials for molding into, for instance, fibers and films. Moreover, they are reinforced with fillers such as glass fibers for making the best use of these characteristics. However, polyolefins have low adhesion to glass fibers and thus it is not possible to sufficiently enjoy reinforcing effects of fillers, because they are free of reactive functional groups. To eliminate these disadvantage, there have been proposed the use of so-called modified polyolefin resins such as those obtained through copolymerization of olefins with modifying agents, for instance, unsaturated carboxylic acids or epoxy group-containing vinyl monomers such as giycidyl methacrylate (hereinafter referred to as "GMA") or allyl glycidyl ether, or grafting polyolefin resin with the modifying agents (see, for instance, Japanese Unexamined Patent Publication (hereinafter referred to as "J. P. KOKAI") No. Sho 59-62613).
According to these methods, strong chemical bonds are formed between carboxyl groups or epoxy groups and glass fibers and thus the glass fibers are firmly adhered to the modified polyolefin resin. More specifically, the reinforcing effect by glass fibers is improved in systems which these modified polyolefin resins are used. However, the modification with unsaturated carboxylic acids possibly becomes a cause of corrosion of metallic parts such as screws of an extruder during the preparation of fiber-reinforced resins. In addition, the epoxy group-containing vinyl monomers, in general, have a low boiling points often give out a bad smell during extrusion at a high temperature and thus have bad workability.
Moreover, it has been investigated to blend polyolefin resins with other resins such as polyester resins, polyphenylene sulfide resins, polycarbonate resins and polyamide resins since they are excellent in impact resistance and resisance to chemicals and are not expensive. However, the polyolefin resin in itself has low compatibility with the foregoing resins. Accordingly, the resulting blend shows substantial reduction of such properties as Izod impact strength, tensile strength and elongation and is not impracticable.